The present invention relates to an arrangement for holding and cooling work pieces that are placed next to one another, and to a method for coating the work pieces placed in the arrangement, with a slide coating of a selected hardness.
European patent document EP-PA 0 272 447, which is equivalent to U.S. Pat. No. 4,889,772, discloses a method for the production of a composite material such as a slide coating on bearing shells. An apparatus which can be used to practice this method, but which is not part of the prior art, has a groove-shaped surface into which the bearing shell blanks to be coated are placed and pressed using one margin shoulder. Each margin shoulder is screwed tight to a longitudinal side of the groove-shaped surface. The base of the groove-shaped surface is cooled through a longitudinal bore at the bottom of the wall of the arrangement, if possible along a line. Hereby on the apex of the bearing shells adjacent the base, fine particles with a high surface hardness are deposited and toward the margin, coarse particles with a correspondingly lesser surface hardness are deposited. Bearing shells with such a hardness distribution have an especially high serviceable life.
Placement of the work pieces could take place either inside the vacuum chamber or outside in the case of arrangements which are screwed out of the vacuum chamber. If the arrangement was screwed out of the vacuum chamber this was, on the one hand, time-consuming and cumbersome. In addition, care had to be taken that no cooling fluid ran into the vacuum chamber. Placing the work pieces in the vacuum chamber in order to avoid having the cooling fluid run out was possible, however, hereby the processing time for each coated work piece was increased due to the idle time of the vacuum coating chamber.
Another arrangement described in German patent document DE-OS 37 17 712, which is equivalent to U.S. Pat. No. 4,891,009, allows the work pieces to be placed into a work piece holder outside of the vacuum coating chamber. In the work piece holder a hollow space filled with cooling means and extending approximately over the entire bearing surface of the bearing shells is available for heat storage. Special measures are taken in order to carry off the heat absorbed by the heat storage during the coating process on a head part of the work piece holding means. To improve the temperature constancy during the coating process a metal shell with good heat transmission is used as the bearing surface for the bearing shell blanks. Good heat transmission is achieved through fins, wires or strips.
The arrangement described in DE-OS 37 17 712 does indeed allow placement of the work pieces outside of the vacuum chamber, however, the apparatus is heavy and consequently cumbersome.